public class Singleton {private volatile static Singleton instance;public static Singleton getInstance () {if (instance == null) {synchronized (Singleton.class) {if (instance == null) {instance = new Singleton();}}}return instance;}
}

class Singleton {private:volatile Singleton* pInst = 0;public:static Singleton* GetInstance() {if (pInst == 0) {lock();if (pInst == 0) {pInst = new Singleton();}unlock();}return pInst;}
}

3、总结